Research: Can Disc Herniations Actually Be Worse Than The MRI Shows? Part 1

Thursday, June 30th, 2016
Woman in MRI machine talking with doctor about MRI results

A question I have asked myself over the years is, “Yes, this patient has a low back disc herniation of 4 mm (or whatever it may be) when laying down in a tube doing an MRI but…what happens to that disc when a person sits up or bends over while bearing weight?”

This is a valid question when you consider that I have seen patients with classic disc signs including radiculopathy into one or more feet. Understand that a general rule with radiculopathy is that the further beyond the knee it extends, the more likely it is to be a disc causing the symptom. In these patients, when you have several other orthopedic signs pointing to a disc, you would reasonably expect a mild to moderate, or possibly a severe, disc bulge.

I’m here to tell you that it doesn’t always go that way. So, again, I find myself asking the question.

The disc can be likened to a really strong bag of water. If I lean one direction, I will push the bulk of the “water” in the opposite direction and vice versa. Also consider that the most pressure you can put on your lower back is to be in the seated position or seated and bending forward position. What exactly do these positions and loads do to a disc that is already at 4 mm when simply lying down without bearing any weight on it?

Well, what do we do when we have questions? We turn to research and thank goodness I’m not the only one that felt this was an important question to figure out!

As a matter of fact, I found so many research papers on this topic, I am going to break the discussion (and blogs) into separate parts to make it easier to digest and not quite so boring.

So here goes Part 1. We’ll start by a study by Nguyen et. al called “Upright magnetic resonance imaging of the lumbar spine: Back and Pain Radiculopathy.”

Why They Did It

While low back pain and pain into the legs or numbness and tingling into the legs may be somewhat common, many times the findings on an MRI don’t show what we would expect to see. The authors of this study wanted to find out what difference there would be in a supine, (lying down) MRI vs. an MRI performed with the patient in a seated position bearing weight (axial loaded).

How They Did It

  • There were a total of 17 participants.
  • 10 of the participants were asymptomatic.
  • Seven of the participants were symptomatic.
  • Upright MRI was done on each adult while they were in the seated position.
  • Measurements were performed from the second and third lumbar level (beginning of the low back) down to the fifth lumbar and tailbone region.
  • There were also measurements of the areas the nerves of the low back pass through to determine the various sizes of these holes, also known as foramen.

What They Found

  • Mid-disc width accounted for 56% of the maximum foramen with in the symptomatic group.
  • Mid-disc width was over 63% of the maximum foramen within asymptomatic volunteers.
  • Disc bulging was 48% larger in the symptomatic group.
  • The measurements of the foramen were smaller in the symptomatic group.

Wrap It Up

The information suggests that MRIs performed in the upright seated position can be useful in the diagnosis process because it is better able to distinguish important differences among the asymptomatic and symptomatic. Especially in regards to the size of the intervertebral foramen.

Nguyen HS, et al. “Upright magnetic resonance imaging of the lumbar spine: Back pain and radiculopathy.” J Craniovertebr Junction Spine. 2016 Jan-Mar;7(1):31-7.

In another study by Madsen, et. al., while the authors argue that axial loading of the spine does not necessarily cause any significant changes to the disc itself, the simple act of having more extension in the spine was a determining factor as to how much space remained in the dural sac surrounding the spinal cord or cauda equina.

I wanted to be fair so I included this study. It suggests the discs play a very small part in the process but, as you will see from approximately 10 other papers we’ll discuss, this sort of finding or thought process is very much in the minority.

Madsen R, et al. “The effect of body position and axial load on spinal canal morphology: an MRI study of central spinal stenosis.” Spine (Phila Pa 1976). 2008 Jan 1;33(1):61-7.

In yet another similar study (Hansson, et. al.) the authors were testing similar parameters in the cases of diagnosed stenosis patients.

Why They Did It

Protrusion of a disc has commonly been cited as the cause of symptoms from nerve root compression in patients with stenosis when the spine was axially loaded (weight-bearing). They were interested in determining whether it is the disc or the ligamentum flavum that caused the difference when loaded.

How They Did It

  • There were 24 participants in the study.
  • The lumbar (low back) spines were examined by MRI while lying down supine (face up).
  • Then the study was repeated with roughly half of their weight loaded to the spine axially.
  • The measurements were through the cross-sectional areas of the spinal canal as well as the ligamentum flavum, the thickness of the ligamentum flavum, the posterior bulge of the disc and the intervertebral angle.

What They Found

  • The axial loading did in fact decrease the cross-sectional size of the spinal canal.
  • Increased bulge or thickening of the ligamentum flavum was to blame for 50%-85% of the decrease in the spinal canal size.

Wrap It Up

The authors concluded that it appears the ligamentum flavum, not the disc, played a dominate role in reducing the size of the spinal canal on axially loaded spines for those with stenosis.

Hansson T, et al. “The narrowing of the lumbar spinal canal during loaded MRI: the effects of the disc and ligamentum flavum.” Eur Spine J. 2009 May;18(5):679-86.

That’s going to wrap it up for this week. We will continue with Part II next week.

I hope you’re learning something here. We’re scratching the surface but, when interpreting your lower back MRIs, keep in mind that unless you had a weight-bearing MRI, you may not be getting the whole story.

by Jeff S. Williams, D.C.
Chiropractors in Amarillo
Spinal Decompression Amarillo
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